dbcve.org
SafariWeb browser · Apple

CVE-2021-30720

MEDIUM · 5.4 CVSS v3.1 Published 2021-09-08
Fix available
A fix is available. Upgrade to 7.5 / 11.4 or later.
See remediation →
61/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A logic issue was addressed with improved restrictions. This issue is fixed in tvOS 14.6, iOS 14.6 and iPadOS 14.6, Safari 14.1.1, macOS Big Sur 11.4, watchOS 7.5. A malicious website may be able to access restricted ports on arbitrary servers.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A logic flaw in Safari's port restriction handling allowed malicious websites to bypass same-origin policy restrictions and access restricted ports on arbitrary servers. The vulnerability stemmed from inadequate validation of port access controls.

MitigationApply the vendor-supplied patches for the affected Apple operating systems (iOS 14.6+, iPadOS 14.6+, tvOS 14.6+, watchOS 7.5+, macOS Big Sur 11.4+) and Safari (14.1.1+) to restore proper port access restrictions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SafariWeb browser
Affected:< 14.1.1
IpadosOperating system
Affected:< 14.6
Iphone OsOperating system
Affected:< 14.6
macOSOperating system
Affected:>= 11.0.1, < 11.4
TvosOperating system
Affected:< 14.6
WatchosOperating system
Affected:< 7.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Safari or WebKit browser usage
    Confirm you are using Safari or a WebKit-based browser (such as Safari on macOS, iOS, iPadOS, or WebKit browsers on Apple TV/Apple Watch). Check the browser application name and ensure it is Safari or a browser that uses Apple's WebKit rendering engine.
    Affected if The browser in use is Safari or a WebKit-based browser on an affected Apple platform.
  2. Check Safari version on macOS
    Open Safari, click Safari in the menu bar, then select About Safari. Compare the version number displayed to the affected range (versions prior to 14.1.1).
    Affected if Safari version is older than 14.1.1 on macOS.
  3. Check iOS version on iPhone
    On iPhone, go to Settings > General > About. Note the iOS version number. Compare it to the affected range (versions prior to 14.6).
    Affected if iOS version is older than 14.6 on iPhone.
  4. Check iPadOS version on iPad
    On iPad, go to Settings > General > About. Note the iPadOS version number. Compare it to the affected range (versions prior to 14.6).
    Affected if iPadOS version is older than 14.6 on iPad.
  5. Check macOS version
    Click the Apple menu > About This Mac. Note the macOS version (such as Big Sur 11.x). Compare to the affected range (11.0.1 through versions older than 11.4).
    Affected if macOS version is 11.0.1 or later but earlier than 11.4.

You are affected if you use Safari or a WebKit-based browser on any Apple device running software versions older than the patched releases (Safari 14.1.1+, iOS/iPadOS 14.6+, tvOS 14.6+, watchOS 7.5+, or macOS 11.4+).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 7.5 / 11.4 / 14.1.1 or later
Fixed in 7.511.414.1.1
Interim mitigation

Apply the vendor-supplied patches for the affected Apple operating systems (iOS 14.6+, iPadOS 14.6+, tvOS 14.6+, watchOS 7.5+, macOS Big Sur 11.4+) and Safari (14.1.1+) to restore proper port access restrictions.

Recommended fix High confidence

Product-specific: Safari 14.1.1, iOS 14.6, iPadOS 14.6, macOS Big Sur 11.4, tvOS 14.6, or watchOS 7.5

  1. Identify the affected Apple product (Safari, iOS, iPadOS, macOS, tvOS, or watchOS)
  2. Check the current version of the product via Settings > General > About or the Safari > About menu
  3. For Safari on macOS: Upgrade to Safari 14.1.1 or later
  4. For iPhone: Upgrade to iOS 14.6 or later
  5. For iPad: Upgrade to iPadOS 14.6 or later
  6. For Mac: Upgrade to macOS Big Sur 11.4 or later
  7. For Apple TV: Upgrade to tvOS 14.6 or later
  8. For Apple Watch: Upgrade to watchOS 7.5 or later
Caveat Standard minor OS/browser upgrade risks apply (rare app compatibility issues, settings reset)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Safari Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-30720 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data